2,670 research outputs found
Optimal control of multiscale systems using reduced-order models
We study optimal control of diffusions with slow and fast variables and
address a question raised by practitioners: is it possible to first eliminate
the fast variables before solving the optimal control problem and then use the
optimal control computed from the reduced-order model to control the original,
high-dimensional system? The strategy "first reduce, then optimize"--rather
than "first optimize, then reduce"--is motivated by the fact that solving
optimal control problems for high-dimensional multiscale systems is numerically
challenging and often computationally prohibitive. We state sufficient and
necessary conditions, under which the "first reduce, then control" strategy can
be employed and discuss when it should be avoided. We further give numerical
examples that illustrate the "first reduce, then optmize" approach and discuss
possible pitfalls
From Individual to Collective Behavior of Unicellular Organisms: Recent Results and Open Problems
The collective movements of unicellular organisms such as bacteria or amoeboid (crawling) cells are often modeled by partial differential equations (PDEs) that describe the time evolution of cell density. In particular, chemotaxis equations have been used to model the movement towards various kinds of extracellular cues. Well-developed analytical and numerical methods for analyzing the time-dependent and time-independent properties of solutions make this approach attractive. However, these models are often based on phenomenological descriptions of cell fluxes with no direct correspondence to individual cell processes such signal transduction and cell movement. This leads to the question of how to justify these macroscopic PDEs from microscopic descriptions of cells, and how to relate the macroscopic quantities in these PDEs to individual-level parameters. Here we summarize recent progress on this question in the context of bacterial and amoeboid chemotaxis, and formulate several open problems
Reaction Networks and Population Dynamics
Reaction systems and population dynamics constitute two highly developed areas of research that build on well-defined model classes, both in terms of dynamical systems and stochastic processes. Despite a significant core of common structures, the two fields have largely led separate lives. The workshop brought the communities together and emphasised concepts, methods and results that have, so far, appeared in one area but are potentially useful in the other as well
A survey of random processes with reinforcement
The models surveyed include generalized P\'{o}lya urns, reinforced random
walks, interacting urn models, and continuous reinforced processes. Emphasis is
on methods and results, with sketches provided of some proofs. Applications are
discussed in statistics, biology, economics and a number of other areas.Comment: Published at http://dx.doi.org/10.1214/07-PS094 in the Probability
Surveys (http://www.i-journals.org/ps/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Structure preserving schemes for the continuum Kuramoto model: phase transitions
The construction of numerical schemes for the Kuramoto model is challenging
due to the structural properties of the system which are essential in order to
capture the correct physical behavior, like the description of stationary
states and phase transitions. Additional difficulties are represented by the
high dimensionality of the problem in presence of multiple frequencies. In this
paper, we develop numerical methods which are capable to preserve these
structural properties of the Kuramoto equation in the presence of diffusion and
to solve efficiently the multiple frequencies case. The novel schemes are then
used to numerically investigate the phase transitions in the case of identical
and non identical oscillators
Balancing Related Model Order Reduction Applied to Linear Controlled Evolution Equations with LĂ©vy Noise
Otto-von-Guericke-Universität Magdeburg, Fakultät für Mathematik, Dissertation, 2016von Martin Redmann, M. Sc.Literaturverzeichnis: Blatt 177-18
- …